Ableist comment from incompetent SSV

There's a SSV at our store known for just doing things wrong. This SSV does not have the confidence to run a floor, and I hate the days I have to open after their closes and clean up all the messes and mistakes they leave behind. This person is just as new as I am, so I've tried to be really patient and pleasant when I talk to them, but it's hard because my only interaction is usually changing shifts and knowing all the extra work they've made for the store time after time after time.

Today I had a very short exchange with the SSV that made me uncomfortable:

SSV- how has business been today?

Me- it's been very slow this morning actually.

SSV- slow as in a handicapped person or slow paced?

Me- ...business has been slow paced.

SSV - oh, so still like a handicapped person then.

Me- ummm.. no. I don't think that's appropriate to say at all.

SSV- I have a cousin with cerebral palsy and he's in a wheelchair so it's totally cool if I say that!

Me- no. It's not appropriate for anyone to.

Mind you we had this conversation as I was getting something from the pastry case and there were lots of customers around!! It just blew my mind that this person in authority would make such an unnecessary/insensitive/ blatantly rude comment!!! And I already don't like this SSV!! Certainly don't want to give them another chance now. If this happens again, should I tell somebody?